Abstract Very few studies have targeted weight control in preschoolers even though the prevalence of overweight has exceeded 20% in this age-group for the past decade. Also concerning is that few studies have focused on preschoolers from low-socioeconomic (SES) backgrounds despite persistent obesity-related socioeconomic disparities. Family-based, behavioral interventions appear a promising model for treatment of obesity in early childhood. However, the dissemination potential of these programs is unclear as they have primarily been tested with families from middle-to-upper class backgrounds and within research settings. Identifying effective approaches to weight control for preschoolers from low-SES backgrounds that can be delivered in community settings is imperative to reducing the pediatric obesity epidemic. The proposed study will begin to address this critical gap by completing the second phase of developing a community-based preschool weight control intervention for families enrolled in the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC). The proposed study is significant because we specifically target preschool weight control in a high-risk population and because delivery of our program within the WIC program is conducive to its dissemination. In preparation for this application, we conducted a formative study with families of overweight and obese preschoolers enrolled in WIC to determine how to adapt existing preschool obesity interventions to meet their needs. Based upon our formative work, and existing preschool obesity programs, we have developed a 12-session, community and family-based preschool weight control intervention (FBWC) that emphasizes experiential learning and is delivered in the WIC and home settings. Sixty overweight and obese preschool-caregiver dyads will be randomized in a 2:1 ratio to receive FBWC or to continue with standard of care at WIC (WSOC). The primary study aims are to a) examine the feasibility and acceptability of FBWC and b) explore the preliminary efficacy of FBWC compared to WSOC on reduction in preschooler BMI-z-score and caregiver BMI from baseline to post-treatment (3-months) and 6-months (3-month follow-up). An exploratory aim is to evaluate lifestyle and behavioral indicators of intervention success. A mixed-methods approach (semi- structured qualitative, individual interviews and quantitative measure) will be applied to assess specific aim one. Preschooler and caregiver height and weight will be collected at baseline, 3-, and 6-months to evaluate specific aim two. The following data will also be gathered at baseline, 3-, and 6-months to evaluate our exploratory aim: preschooler and caregiver diet and physical activity, caregiver stress, and home food environment. This study is innovative because: 1) very few studies have examined obesity intervention in preschoolers, 2) we target weight control in a high-risk group that has been underrepresented in the preschool obesity treatment outcome literature, 3) our intervention is community-based, and 4) we emphasize experiential learning as a strategy for achieving lifestyle behavior change and weight control.